Empty StarWars Widget

class.StarWarsWidget.php

<?php

/**
 * Adds StarWarsWidget widget.
 */

class StarWarsWidget extends WP_Widget {

	/**
	 * Register widget with WordPress.
	 */
	public function __construct() {
		parent::__construct(
			'wcms18-starwars-widget', // Base ID
			'WCMS18 StarWars', // Name
			[
				'description' => __('A Widget for displaying some StarWars trivia', 'wcms18-starwars-widget'),
			] // Args
		);
	}

	/**
	 * Front-end display of widget.
	 *
	 * @see WP_Widget::widget()
	 *
	 * @param array $args     Widget arguments.
	 * @param array $instance Saved values from database.
	 */
	public function widget($args, $instance) {
		extract($args);
		$title = apply_filters('widget_title', $instance['title']);

		// start widget
		echo $before_widget;

		// title
		if (! empty($title)) {
			echo $before_title . $title . $after_title;
		}

		// content
		echo "Here be some StarWars trivia.";

		// close widget
		echo $after_widget;
	}

	/**
	 * Back-end widget form.
	 *
	 * @see WP_Widget::form()
	 *
	 * @param array $instance Previously saved values from database.
	 */
	public function form($instance) {
		if (isset($instance['title'])) {
			$title = $instance['title'];
		} else {
			$title = __('StarWars Trivia', 'wcms18-starwars-widget');
		}

		?>

		<!-- title -->
		<p>
			<label
				for="<?php echo $this->get_field_name('title'); ?>"
			>
				<?php _e('Title:'); ?>
			</label>

			<input
				class="widefat"
				id="<?php echo $this->get_field_id('title'); ?>"
				name="<?php echo $this->get_field_name('title'); ?>"
				type="text"
				value="<?php echo esc_attr($title); ?>"
			/>
		</p>
		<!-- /title -->
	<?php
	}

	/**
	 * Sanitize widget form values as they are saved.
	 *
	 * @see WP_Widget::update()
	 *
	 * @param array $new_instance Values just sent to be saved.
	 * @param array $old_instance Previously saved values from database.
	 *
	 * @return array Updated safe values to be saved.
	 */
	public function update($new_instance, $old_instance) {
		$instance = [];

		$instance['title'] = (!empty($new_instance['title']))
			? strip_tags($new_instance['title'])
			: '';

		return $instance;
	}

} // class StarWarsWidget

wcms18-starwars.php

<?php
/**
 * Plugin Name: WCMS18 StarWars Widget
 * Plugin URI:  https://thehiveresistance.com/wcms18-starwars
 * Description: This plugin for displaying some StarWars trivia.
 * Version:     0.1
 * Author:      Johan Nordström
 * Author URI:  https://thehiveresistance.com
 * License:     WTFPL
 * License URI: http://www.wtfpl.net/
 * Text Domain: wcms18-starwars
 * Domain Path: /languages
 */

require("class.StarWarsWidget.php");

function wsw_widgets_init() {
	register_widget('StarWarsWidget');
}
add_action('widgets_init', 'wsw_widgets_init');